Starting Problems

Your graphic card is a bit old, maybe try to download latest drivers from here: http://support.amd.com/en-us/download

There are other workarounds in this page:

If you’ve tried reinstalling the game, make sure that you delete the game folder manually, since Steam sometimes leaves files behind.

If updating the drivers doesn’t work, make sure to try the workarounds in that post, as they have helped some users. I can suggest more things to try if none of them work for you.